From: Pavel Begunkov <asml.silence@gmail.com>
Date: Thu, 20 Aug 2020 08:34:10 +0000 (+0300)
Subject: io_uring: comment on kfree(iovec) checks
X-Git-Tag: baikal/aarch64/sdk6.1~8531^2~1
X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=8ed80d293382821dca8c8f243d5cfe5e1a67db36;p=kernel.git

io_uring: comment on kfree(iovec) checks

kfree() handles NULL pointers well, but io_{read,write}() checks it
because of performance reasons. Leave a comment there for those who are
tempted to patch it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index d43a20a554e4c..b9ca5a54dc204 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3204,6 +3204,7 @@ done:
 	kiocb_done(kiocb, ret, cs);
 	ret = 0;
 out_free:
+	/* it's reportedly faster than delegating the null check to kfree() */
 	if (iovec)
 		kfree(iovec);
 	return ret;
@@ -3300,6 +3301,7 @@ copy_iov:
 			return -EAGAIN;
 	}
 out_free:
+	/* it's reportedly faster than delegating the null check to kfree() */
 	if (iovec)
 		kfree(iovec);
 	return ret;